Effect of Protein Energy Malnutrition on the Lipid Composition and Leucine Uptake of Small Intestinal Brush Border Vesicles of Growing Rhesus Monkeys

Abstract

Mild to moderate protein energy malnutrition (PEM) was induced in young developing rhesus monkeys by giving them half of the casein-based synthetic diet which was given to control animals. After a body weight reduction of 30-40%, the PEM animals were sacrificed. The small intestine was removed, flushed with ice-cold saline, everted and divided into equal proximal, middle and distal segments. Brush border membrane vesicles (BBMV) were prepared from all three segments and assayed for marker enzymes, e.g. sucrase and alkaline phosphatase, to assess their purity. Sucrase was found to be purified 23-fold and alkaline phosphatase 12-fold compared to the respective homogenates in all three parts. In PEM animals, uptake of [U-¹⁴C]L-leucine into the BBMV was diminished in all three segments and cholesterol and phospholipid levels also decreased significantly. As a result there was an elevation in the molar ratio of cholesterol to phospholipid, and the sphingomyelin: phosphatidylcholine molar ratio also increased. This signified a decrease in lipid fluidity and amino acid uptake in PEM in the small intestine. Histologically, a mild to moderate grade of partial villus atrophy was observed in the intestine. The diminished uptake and lipid fluidity of the membrane and the histological changes returned to their control values after nutritional rehabilitation.

Mild-to-Moderate Malnutrition Alters Glutathione, Gamma-Glutamyl-Transpeptidase and Glycine Uptake in Small Intestinal Brush-Border Vesicles of Rhesus Monkeys

“…Therefore, the findings of the present study cannot be compared. But similar decrease was observed in case of leucine uptake by small intestine in the same model from our lab [5].…”

“…The reversal of GGTP activity and uptake of U-14 Cglycine, observed on nutritional rehabilitation, might be due to recovery of intestinal architecture on rehabilitation [5].…”

“…In the present study, significantly decreased glutathione content might be responsible for decrease in the amino acid uptake even with the increase in GGTP activity in experimental group. Further the decreased uptake of U-14 C-glycine in small intestinal segments may also be due to partial villus atrophy and/or significantly increased molar ratios of cholesterol to phospholipids and sphingomyelin to phospatidyl choline [5]. The increased molar ratios of cholesterol to phospholipid correspond to decreased lipid fluidity of the membrane hence decreased uptake of U-14 C-glycine.…”

“…Decrease in enzyme activities [4] and uptake of L-leucine in protein-energy malnutrition have been observed [5]. Alternations in the permeability characteristics of the enterocytes have also been documented in undernutrition.…”

“…Any damage to small intestinal mucosa may affect the enzyme activity. Protein energy malnutrition (PEM) is known to affect the normal architecture of small bowel [5]. Hence, determination of GGTP activity, reduced glutathione content and uptake of amino acid is very important.…”